Mark. — Lepidosteus. 



ABBREVIATIONS. 



cap. Head of villus. pd. Stalk of villus. 



c.-t. cp. Connective-tissue corpuscle, rx. Root of villus. 



fits. mat. Maturation spindle. st. vil. Villous layer of egg membrane. 



gran. Granulosa. th.fol. Membrana propria of thecafolliculi. 



m py. can. Micropylar canal. vac. Vacuole. 



m py. cl. Micropylar cell. vit. Vitellus. 



nl. Nucleus. vs. g. Germinative vesicle. 



nl. gran. Nucleus of granulosa cell. z. r. Zona radiata. 



PLATE IX. 



Fig. 1. Section of an ovarian egg about 6 mm. in diameter tbrough tbe ger- 

 minative vesicle. The villous layer is at all points in contact with 

 the yolk ; but it is separated from the granulosa at intervals. The 

 egg was hardened in 0.25 per cent chromic acid and stained in alco- 

 holic borax-carmine. X 158. 



" 2. Portion of a radial section through a mature ovarian ovum, hardened in 

 0.25 per cent chromic acid, showing the penetration of tbe roots of 

 the villi into the pore-canals of the zona radiata. X 515. 



" 3, 4. Radial sections of ovarian eggs preserved in alcohol, showing stages 

 in the formation of the villous layer. The eggs were somewhat more 

 than 0.5 mm. in diameter, and were stained in alcoholic borax-car- 

 mine. X 510. 



" 5. A portion of Figure 1 enlarged. The outlines of the granulosa cells, 

 especially on the side toward the villi, are much too sharp. X 515. 



